1. Field of Invention
The present invention relates to machine vision and, more specifically, to a system and method for improving image processing using a reflective background.
2. Description of Prior Art
Machine vision plays an important role in automated and robotic systems, such as assembly line manufacturing, quality control inspection, and sample processing. Conventional systems are generally comprised of a optical imager, such as a charged coupled device (CCD) or similar device using digital imaging technology, that is positioned capture images of objects that pass in front of it. In low-light or enclosed applications, machine vision systems may include an illumination source, such as a bank of light emitting diodes (LEDs), positioned proximately to the imager. The images are subsequently processed to decode information contained in the resulting two-dimensional image, such as 1D linear codes, 2D stacked/matrix codes, OCR fonts, and postal codes. The image captured by the machine vision system may also be subjected to more advanced processing, such as shape recognition or detection algorithms, that provide information about the object of interest in the image. However, the characteristics of digital images taken by machine vision systems, such as the contrast of the image, often limit the processing techniques that may be employed and adversely affects the accuracy of the results obtained from the processing of the image contents.
Some attempts to improve the quality of images obtained by machine vision systems involve the use of sophisticated lighting systems to improve the digital image captured by the system. For example, the illumination source may comprise multiple banks or arrays of LEDs that completely encircle the targeted object. While such a system is useful for solitary, immobile objects, it is not as effective for illuminating objects in motion and requires a plethora of expensive components.
Other attempts to more completely capture the digital image of an object in a machine vision system include the addition of a second light source or second imager for illuminating the object. For example, a second light source positioned adjacent to the imager and the associated primary light source, or a second light source positioned on the opposite side of the object to be imaged will increase the amount of light reflected by the object, thereby improving the quality of a digital image taken of the object. Imaging systems using sophisticated illumination banks or arrays require additional components that increase the cost of the machine vision system, need additional circuitry for controlling the dual illumination sources or imagers, and require a large footprint in the assembly line or process where they are used.